It is known that the resistance of a thin metal film can be reversibly tuned via the application of an external charge in an electrolyte where the Helmholtz double layer is utilized as the gate electrode. In this context, the idea of an electrochemically gated all-metal device is related to the well known field-effect transistor (FET), where the electronic transport through a semiconductor channel is controlled by an external gate potential.
However, the effect, i.e., the change in resistance (ΔR/R) is only about 1-2% in the case of a pure metal due to a very large intrinsic carrier density and very short screening length resulting from the very large intrinsic carrier density. This restricts the selection of the pure metal to materials that are stable in an electrochemical environment, which are inert, noble metals and are extremely expensive and heavy. The size of the surface charge induced variation during electronic transport in a metallic conducting material increases with an increase in surface-to-volume ratio. However, most metallic materials with very high surface-to-volume ratio, such as de-alloyed metals, are not thermodynamically stable. Any supply of external energy thus reduces the surface area and the size of surface related effects. Accordingly, a material which could be used in these electrochemical environments and remain stable and do not suffer from the deficiencies of inert, noble metals would be very beneficial.